Aluminium-bronze alloy



United States Patent 3,551,144 ALUMINIUM-BRONZE ALLOY Norman Coupe Ashton, Corby, Birkby Road, Huddersfield, Yorkshire, England, and John P. Dennison, 1 Channel View Sketty, Swansea, Glamorgan, Wales No Drawing. Filed Dec. 6, 1967, Ser. No. 688,304 Claims priority, application Great Britain, Dec. 7, 1966, 54,760/ 66 Int. Cl. C22c 9/00 U.S. Cl. 75-162 1 Claim ABSTRACT OF THE DISCLOSURE An aluminium-bronze alloy contains 8% to 9% aluminium or aluminium equivalent and sufficient boron (preferably in the range 0.01% to 0.02%) to create nucleation of the beta phase during cooling of the alloy before the creation of the alpha base. This facilitates removal of the beta regions in subsequent heat treatment.

This invention relates to aluminium bronze alloy, and the object of the invention is to provide an aluminium bronze alloy of refined grain structure which, in consequence of its grain structure, is inherently strong and combines the advantages of responding well to hot working in the alpha-i-beta range whilst after a suitable heat treatment being capable of extensive cold working.

According to this invention an aluminium-bronze alloy contains 8%-9% aluminium (or aluminium equivalent) and sufficient boron to create nucleation of the beta phase during the cooling of the alloy before the creation of the alpha base.

Since in certain aluminium bronzes it is desirable to include small additions of tin it is to be understood that the term aluminium equivalent is used herein to describe aluminium or a mixture of aluminium and tin as it is the aluminium equivalent which will determine response to nucleation by boron.

It is preferred that the aluminium equivalent shall be present in the range 8.2% to 8.6%, since the addition of boron is most effective in the nucleation of the beta phase within this range. It is thought that by promoting beta nucleation, the boron prevents the presence of large regions of beta in the final cast structure. More particularly, it appears to be effective in preventing the formation of wide bands of the easily deformed beta phase when the alloy is subjected to an extrusion process.

Patented Dec. 29, 1970 It is also preferred that the boron shall be present in the range 0.01% to 0.02%, although larger amounts could be used if desired.

Without boron, the alloy is hypoeutectic, so that the alpha phase would form first and beta would deposit as a coarse eutectic constituent. With the addition of boron (in the specified range of aluminium equivalent) the beta phase is formed as a fine well dispersed pro-eutectic dendrites. This facilitates the removal of the beta regions in subsequent heat treatment and thus improves subsequent cold workability.

Apart from the creation of an inherently stronger alloy than known aluminium-bronzes, it is possibly by use of the invention to avoid use of appreciable amounts of iron in the alloy. Iron has been used previously in quantities from 1.5% to 3.5% in order to refine the cast grain structure. However, the iron presents a serious disadvantage if the material has to be softened to a very low hardness for cold working, because if there is an appreciable iron content, the hardness remains high despite heat treatment and annealing.

A typical alloy in accordance with the invention has the following composition:

Aluminium equivalent: 8.4% Boron: 0.02% Copper: Balance.

We claim:

1. An aluminiumbronze consisting essentially of 8 to 9% aluminium, 0.01 to 0.02% boron and the balance copper, said alloy characterized by an alpha plus beta microstructure wherein the beta phase is formed as fine well dispersed pro-eutectic dendrites.

References Cited UNITED STATES PATENTS 1,076,973 10/1913 Gleason -162 3,416,915 12/1968 Mikawa 75162 FOREIGN PATENTS 537,225 6/ 1941 Great Britain 75154 CHARLES N. LOVELL, Primary Examiner U.S. Cl. X.R. 

